1. Field of the Invention
The present invention concerns an eyeglass lens display unit for use by an optometrist.
2. Description of the Prior Art
For displaying eyeglass lenses, optometrists currently use lorgnettes which comprise a circular frame accommodating an eyeglass lens and are usually pivotally mounted on a display plate.
U.S. Pat. No. 1,547,142 describes one embodiment of a lorgnette of the above kind.
U.S. Pat. No. 5,467,869 discloses an eyeglass lens display case which includes a plate adapted to receive an eyeglass lens to be displayed and two half-shells which are pivotally mounted at the edge of the plate and each of which can move between a closed position in which they conjointly form a protective shell for the plate and an open position in which they uncover it.
The major disadvantage of such display units is that they can display only one eyeglass lens at a time.
There already exists a display lens for demonstrating the effectiveness of anti-reflection treatment of an eyeglass lens in which only the center of the display lens has received the anti-reflection treatment.
Finally, there is already known in the art a plane display unit with slots into which various eyeglass lenses cut in half along a diameter are inserted.
However, with a plane display unit of the above kind, it is complicated to compare two different lenses because this requires the lenses to be manipulated, in particular extracted from the display unit.
A display unit of the above kind is also relatively bulky and impractical.
To overcome the above drawbacks, the present invention proposes a new eyeglass lens display unit comprising at least two branches for supporting at least two different eyeglass lens portions, which branches are mobile relative to each other to position the eyeglass lens portions edge-to-edge along their diameter.
Accordingly, thanks to the display unit according to the invention, an optometrist can easily:
demonstrate the effectiveness of an anti-reflection treatment on one lens portion;
show the difference between the curvatures of the lens portions displayed;
show the difference between the thicknesses of the lens portions displayed; and
show the aspherical nature of the lens portions displayed.
Other advantageous and non-limiting features of the display unit according to the invention are as follows:
the branches are mounted on a plate whose surface facing said branches is adapted to absorb light; this surface is preferably matt black; this shows up better the difference between a lens that has received an anti-reflection treatment and one that has not;
the plate has a flat on its edge, each branch has a flat on the outside edge of its free end and said two flats of said branches when aligned form a single flat parallel to that of said plate and enable said display unit to be placed vertically on a support; a display unit of this kind therefore takes up little room on the desk of an optometrist when positioned vertically;
the branches are articulated to each other by means of a pivot whose axis is perpendicular to the plane containing the branches; in one embodiment of the invention the branches are nested one within the other at one end and the nested ends of said branches incorporate holes for mounting them on the pivot, which can comprise a screw passing through the aligned holes in the branches and screwed into a threaded bush; the branches are easy to handle when articulated in this manner; and
the branches are semicircular.
The following description, which is given with reference to the accompanying drawings, which are provided by way of non-limiting example only, explains the invention and how it can be put into practice.